Agricultural combine harvesters are large machines that harvest, thresh, separate and clean agriculturally cultivated grain-bearing crops. The obtained clean grain is stored in a grain tank arranged on the combine harvester. The threshed straw is usually either chopped and distributed on the field over the width of the cutting unit or conveyed around the straw chopper and deposited on the field in non-chopped form in a windrow in order to be subsequently picked up by a baler. The crop residues ejected out of the rear outlet of the cleaning device such as chaff and small straw particles are distributed on the field by a chaff spreader or conveyed through the straw chopper and distributed on the field.
DE 199 08 111 C1 describes a combine harvester with a straw chopper and two discharge blowers that are arranged laterally adjacent to one another downstream of the straw chopper in order to widely distribute the straw over the field. The outlet of the straw chopper and the inlet of the discharge blowers that are arranged in a housing and feature discharge paddles rotating about an approximately vertical axis are arranged in one plane for the purpose of a material transfer without a change in direction. Casings arranged around the discharge blowers converge in a front point that faces the straw chopper between the discharge blowers. The casings contain cutouts in the rear region in order to deposit the straw on the field. The front sides of the discharge blowers rotate inwardly sides and extend laterally over the straw chopper. The rotational axes are respectively situated in the vicinity of an outer end of the straw chopper. Similar arrangements can also be found in EP 1 269 822 A1, EP 1 277 387 A1, EP 1 514 466 A2 and EP 1 532 858 A1.
This prior art has various disadvantages. The discharge blowers of DE 199 08 111 C1 are relatively large and extends laterally over the straw chopper. This provides the advantage that the discharge blowers receive relatively few crop residues to be initially transported forward in their outer, forwardly rotating regions such that the energy requirement of the discharge blowers remains relatively low, yet large discharge blowers of this type are relatively bulky and elaborate. In contrast to this, the discharge blowers of EP 1 269 822 A1, EP 1 277 387 A1, EP 1 514 466 A2 and EP 1 532 858 A1 have a slightly smaller diameter, yet this has the aforementioned disadvantage that the outer regions of the discharge blowers need to deflect the crop residues impacting at this location by approximately 180° and this deflection is quite energy-consuming. EP 2 036 422 A2 describes a combine harvester with a straw chopper and straw guide plates arranged behind the straw chopper, wherein the crop residue stream is constricted in the lateral direction downstream of the straw chopper such that the straw discharging distance becomes less dependent on the distribution of the crop residues along the shaft of the straw chopper.
US 2007/0015556 A1 describes a combine harvester with a straw chopper, in which the outlet of the straw chopper acts upon the downstream discharge blowers on their periphery from below, namely at an acute angle. WO 2008/156419 A1 describes a similar arrangement of a straw chopper and discharge blowers, but the crop stream is deflected downstream of the straw chopper by means of a plate such that it impacts on the discharge blower in the axial direction, however, at a relatively acute angle. In this case, the central part of the crop residue stream is not deflected as significantly as the outer part such that the speed of the crop residues to be distributed after the discharge from the straw chopper is utilized to the greatest extent possible, namely by acting upon the discharge blowers that rotate inward with their front sides with the outer part of the crop residue stream in front of the rotational axis and throwing the central part of the crop residue stream against the discharge blower rearward of the rotational axis. In this case, it is considered disadvantageous that the deflection of the crop residue stream downstream of the straw chopper leads to friction and therefore energy losses, namely even in the inner regions, in which a relatively small deflection of the crop residue stream takes place.